Created by executive producer Hart Hanson and loosely based on the life and novels of Kathy Reichs, the crime procedural “Bones” stars Emily Deschanel and David Boreanaz as, respectively, forensic anthropologist Dr. Temperance Brennan and FBI Special Agent Seeley Booth. An unlikely pair of crimefighters, the duo have spent the past five years bickering and flirting over any number of gruesome — yet somehow, still amusing — murder investigations and decomposing bodies.

Tonight, during the show’s 100th episode (“The Parts in the Sum of the Whole”) viewers will finally learn the backstory of how Brennan and Booth met for the first time and the case that brought them together. In addition to co-starring, Boreanaz also directed the episode, marking his second time behind the the camera for the series.

Speakeasy recently talked to Hanson, who’s currently in Chicago filming a pilot for the show “Pleading Guilty.” (The pilot is based on the Scott Turow novel and stars Jason Isaacs as a ex-cop-turned-attorney.)

In the 100th episode, we learn a lot about each character’s backstory. Were these details planned from the start of the series, or did they develop more organically?

Hart Hanson: I would say it’s 75% organic. I’m a big fan of letting things unfold as the series goes on, because you learn more about your actors. For example, there’s a part of me that wishes we hadn’t made [lab entomologist Jack] Hodgins so damn rich. It was always part of his character, but once someone’s really rich, the range of problems they face tend to drop.

I actually asked people to go back and make character sketches of each person for the 100th episode, because I’m a very absent-minded man. The trickiest issue was that it looked very much like we met [prosecutor] Caroline [Julian] for the first time in a New Orleans episode, but because the character, who’s played by Patty Belcher, is such a great presence, we wanted her back for the 100th show. To excuse it, we threw in a line where Booth says Brennan never remembers when people are introduced to her. But it’s a cheat because we just wanted Caroline in the show more than we wanted to be strictly religious to the backstory. But boy, if the fans are angry, I’ll find out.

“Bones” fans are indeed a vocal bunch — particularly the “shippers” who think Brennan and Booth should be together. Given that other couples, such as the newly engaged Dr. Sweets and his fiance, on the show are happy, does this mean their relationship is on the backburner?

I know how Booth and Brennan’s story ends. The trick is figuring out where to place it. We talk about it at the least at the beginning, middle and end of every season, as to how we’re going to deal with the hot potato. As for Sweets being happy and what that means for Brennan and Booth, I’ll only say that that’s an excellent way of spotting the seesaw. Hold on to that thought as we go into the season finale.

How does David the director compare with David the actor?

After he did such a good job directing his first episode in season four — and I think he’s always vaguely insulted when I mention he’s a good director — we kind of aimed for him to direct the 100th episode. David as an actor is like a sprinter — energetic and capricious, with short bursts of intense focus. But being a director is more like being a marathoner, and his whole personality changes when he’s in director mode. It’s like you’re talking to a slightly different human being; you recognize the face, handsome face that it is — but it’s a different person. Make me wonder how many personalities he has.

Kathy Reichs, who created the character of Temperance Brennan, is writing her first episode of the show.

I’ve asked her every year if she wanted to write a script, and this year, it worked out. She wrote the second-to-last episode, though I don’t know if it will air there. It’s about witches, which was really fun for us. She had to come sit in the writer’s room, pitch ideas, and bang out an outline, and was fantastic in the room — which I was shocked by, because she’s a novelist. She’s used to working by herself, so it must have been a transition to go into a room of eight powerful personalities, shouting suggestions and putting ideas up on the wall.

A lot of fans have commented that Brennan seems to be regressing as a character. Is that a planned development?

It’s interesting to us because we feel like she hasn’t. On the other hand, I may have failed to get across a phenomenon of her personality, which is that when Brennan becomes pressured emotionally, she tends to go for the super rational — which people can read as regression. But it’s more that she’s being emotionally challenged by Booth more and more. I think that we’ve been very consistent with that.

You’re one of several showrunners listed on “Modern Family” exec producer Steve Levitan’s Twitter page. Are you guys in a secret showrunner cabal?

The “Modern Family” stage is right outside my office window, so Steve and I see each other all the time, because we’re on the same lot, as is David Shore [who runs "House"]. There’s a couple of people that I’ve never met that I tweet back and forth with, such as Bill Prady of “The Big Bang Theory” and Dan Harmon of “Community.” Aziz Ansari, from “Parks and Recreation,” started a little Twitter war with us this season, because we were up against their show and we were beating them in the ratings. He would say things like “Bones” will be doing a blackface episode or that David didn’t like children. Funny stuff, though I think he quickly learned some “Bones” fans don’t have a sense of humor about that sort of thing. It culminated at TCAs [the Television Critics Association], where he said something disparaging about “Bones” at a panel, a journalist immediately Twittered me, I responded, and the journalist threw it back to him on stage. That couldn’t have happened a million years ago, or even five years ago.

How much responsibility do you feel to “Bones” fans on Twitter?

The difficulty is trying not to feel too much responsibility to them. We have 12 million viewers, and let’s say I have almost 20,000 Twitter followers who are my noisiest fans. Those people are a drop in the bucket compared to the overall “Bones” audience. On the other hand, there is something to be said about who the silent majority represents — maybe a mathematician could tell me. The trick is not to let the noisy noisy people have their way. Plus, I’m looking at network testing, our gut feeling, and there’s a network and a studio to consider — there’s a lot of voices who care about the show, and I have to trust me and them as much, or more, than the noise from the Twitter people.

This past winter, the show aired a very pro-”Avatar” themed episode. Since the film, like “Bones” (and the WSJ) are all owned by News Corp, how did the deal come about?

News Corp came to us, and right or wrong, I have to take the hit for it. We get money for that, and since we’re not the highest-budgeted show on TV — we’re okay, but money is tight – I thought if we can get a chunk of money, it might mean that we can go out for more locations or get a bigger guest star. So we just hung a lantern on the fact that we were doing it. And in my bin of ideas, I had always wanted the geeks to geek out somewhere, so that fit into our story. We have a couple other product integrations on the show including Toyota, where the characters on the show drive Toyotas, in exchange for a certain amount of money as well.

Who else is guest-starring in the next two months?

We’ve got Billy Gibbons of ZZ Top {who plays Angela’s father], returning for the season finale. We’ll see [Booth's son] Parker in the finale. We couldn’t get Cyndi Lauper’s [who played a psychic in the season premiere] schedule to line up for a return this season, but we’ll have her back one of these days. Ryan O’Neal [who plays Brennan's father] is also back, and Josh Todd, the lead singer of Buckcherry, guest stars in an episode about a rock and roll fantasy camp.

If the pilot for “Pleading Guilty” is picked up for series, how will you split your time?

Oh, it’ll be brutal. “Bones” is running very smoothly, and my deep desire is to hire a very senior showrunner-writer-producer type to come and work with me on “Pleading Guilty,” so we can do with that show what it took me four years to do on “Bones,” and I can equally look at both sets of scripts. It’ll be be a high-class problem. Statistically, I don’t have to worry about that happening, but it keeps me up at night.

About Speakeasy

Speakeasy is a blog covering media, entertainment, celebrity and the arts. The publication is produced by Barbara Chai and Jonathan Welsh with contributions from the Wall Street Journal staff and others. Write to us at speakeasy@wsj.com or follow us on Twitter at @WSJSpeakeasy or individually @barbarachai.